Monolayer tooling has become an increasingly important construction form for superabrasives, e.g., diamond and cubic boron nitride, replacing the traditional metal, vitreous and resin bonded multi-layered products in many applications and creating entirely new applications for superabrasive material removal. Historically, the principal method of construction of superabrasive monolayer tools was, up until the early 1970's, entrapment electroplating with nickel on a steel or otherwise suitable metallic form. In 1975, a patent was issued to J. T. Lowder et al. for a process of brazing diamond to create mono-layer tools with a nickel-chromium-boron alloy. Other brazing processes had been previously described and used in the manufacture of monolayer abrasive tools. The process invented by Lowder et al. provided an extremely strong, abrasion resistant bond and was commercialized so successfully that it became the principal bonding method for mono-layer diamond abrasive tools in numerous applications and a major competitive method to entrapment nickel plating which previously dominated monolayer abrasive tooling.
Manufacturers of mono-layer abrasive tools have devised various methods for applying the braze alloy and abrasive particles and attempting to control the exposure of the abrasive grains above the bonding layer. The most common quality control method is a simple visual inspection of the finished product at some low magnification, e.g. 5-40.times.. In most instances, a manual inspection against visual standards has been thought to be the most effective technique from both a cost and quality standpoint. Although techniques of topographical mapping and measurement have emerged which would provide precise information regarding abrasive concentration, bond height and abrasive exposure, the expense of such techniques have remained a deterrent to their employment. Not only is there significant capital investment, but the speed of analysis is prohibitively slow with even the best of the advanced topographical scanning systems. Thus, the state of the art in control of abrasive concentration and bond height in monolayer superabrasive tooling is visual inspection of the finished product. Products which fail to meet the visual standard are simply discarded with an accompanying loss of the tool mandrel used in small tools, such as dental drills, and loss of the diamond abrasive particles.
Prior to the present invention, those skilled in the art have failed to provide a method controlling these factors in a practical economic manner.